In a Fibre-Channel (FC) or FC-over-Ethernet (FCoE) storage area network (SAN), servers use Input-Output (IO) read and write requests to access storage arrays over FC/FCoE capable switches in a switch fabric. A data intensive IO request pattern from a server may cause a sudden, short-term traffic burst or spike (referred to as a “microburst”) lasting several milliseconds or even less. As the rate of traffic being received at the switch (perhaps from more than one ingress port) exceeds the destination (egress) link rate, the ingress port(s) will buffer the ingress traffic. Once a finite amount of buffering has occurred, the receiving switch, by various mechanisms, will notify the adjacent transmitting device(s) (end device or switch) to curtail sending subsequent data until notified that the congestion situation has been reduced sufficiently to allow further ingress traffic. This results in network congestion across the switch fabric, which has negative consequences. Note that this can occur even if the end device requesting the data intensive IO request pattern is not itself restricting the flow of data to itself.
Conventional “slow drain” detection indications are absent at the end device because the end device itself is not restricting the traffic flow. However, significant ingress slow drain congestion indications are seen on the “upstream” ingress ports supplying the data. Consequently, ingress congestion is seen without any real egress congestion indications and the end devices causing this situation are not easily detected or identified. Without proper detection or identification, no remediation actions can be taken to reduce the impact.